The invention relates to a method of hot bending a generally straight wire blank of a material being brittle in cold condition, especially a ceramic, refractory resistance material, such as a material consisting substantially of molybdenum disilicide, into a wire element having straight end portions and coils formed therebetween. Such wire elements are particularly useful as glow coils in gas ignition devices or the like.
Hitherto, when manufacturing such wire elements, the coils were formed through hot bending of the wire blank around a mandrel, e.g. of carbon (see e.g., U.S. Pat. No. 3,812,324). This known method, of course, enables a reliable control of the shape of the coils but has the disadvantage of impurities being transferred from the mandrel to the rod element during the hot bending and adversely affecting the quality of the finished rod element.